Lecture 11/12 Flashcards
vessels
what is the circulatory system?
consists of the heart whose function is to pump blood, and the vascualr system of afferent and effeerent blood vessels
what are efferent vessels?
arteries which conduct oxygen and nutrients to the tissues that diffuse out through a capillary network
what are afferent vessesl?
veins which convey to the heart CO2 and waste products of the metabolism of tissues
what are the lymphatics?
anastomotic network of vessesl that start as blind capillaries which converge into large lymphatic vessels and drain into large veins.
what do lymphatic vessels conduct?
lymph, which is plasma enrched with immunoglobulins and lymphocytes, which is produced by phymphatic organs
general plan od blood vessels.
- intima: endothelium (squamous simple epithelium), sub-endothelil layer, IELM (internal elastic lamina)
- Media: elastic membrane and/or smooth muscle (with reticular fibers and proetoglycans between layers)
- adventitia: dense irr. CT, vasa vasorum
special features of the muscular artery
what differentiates it
- 4 or more concentric layers of SM
- 1mm or more in diameter
special features of a middle size vein
what differentiates it
- incomplete media of SM
- collapse lumen
what stain is used to visualize elastic fibers?
verhoeff stain
special features of elastic arteries
- media has concentric layers of SM and elastic membranes
- vasa vasorum
special features of large veins
media contains few layers of SM (4-5 layers) with no elastic membranes
what intermediate fibers are found in vessel SM cells instead of normal SM cells?
vimentin instead of desmin
special featuresof arterioles
- media has 1-2 layers od SM
- diameter is 0.5 mm or less
- has elastic fibers but no ILEM
special features of venule
- absent media
- collapse lumen
- has pericytes
a capillary network is found betwen what?
metaarterioles and postcapillary venules
what are anastomosis?
capillary like vessel between arteriole and venule
role of capillaries
slow down circulation of blood, allowing metabolic exchange between the blood and surrounding tissue:
* exchange
* nutrition
* thermoregulation
* blood pressure regulation
* inflammation
what are the different types of capillaries?
- impermeable/continuous
- permeable - fenestrated
- permeable - sinusoids
where are periocytes often found?
post-capillary venules
function of pericytes
- secrete cytokines
- support
- phagocytic
how are nutrients transported in impermeable capillaries?
via trans-endothelial channels and pinocytic vesicles
where are impermeable capillaries found?
- nervous tissue
- muscle (all)
- skin
- lung
- lymphatics
how are nutrients transported in fenestrated capillaries?
via trans-endothelial channels, pinocytic vesicles, and fenestration/pores with diaphrams
where are fenestrated capillaries found?
- intestinal muscoa
- pancrease
- salivary gland
- endocrine gland
- kidney
how do lipid soluble substances go through capillaries?
diffuse freely
how do small water soluble molecules (<10A) and ions go through capillaries?
through trans-endothelial channels
how do molecules (up to 90A) go through capillaries?
vesicles
how do molecules (more than 90A) go through capillaries?
through pores
how do the hydrostaic pressure and osmotic pressue compare in the arterial end and venous end of the capillary network?
- arterial end: high hydrostatic and low osmotic
- venous: low hydrostatic and high osmotic
general characteristics of lymphatic vessels
how does it compare to blood vessels?
- channels in CT containing lymph (not RBCs)
- very thin endothelial cells (no occluding and gap junctions)
- no BM associated with endothelium
- endothelial cells are anchored to the CT fibers (type I/III collagen, elastic fibers)
what do small or large lymphatic vessels usually have (that small ones don’t)?
valves (fold of the wall projecting into the lumen)
what do large lymphatic vessels have (that smaller ones don’t)
smooth muscle cells in the walls
function of the endothelium
- permeability
- metabolic function (convert angiotensin I into angiotensin II, and inactivate bradykinin, a potentiator of SM contraction, and of serotonin/prostaglandins, NE)
- production of vasoactive substances (endothelin and NO)
- anti-thrombogenic function
endothelin pathway
endothelin binds endothelin receptor, which converts PIP into IP3, which increases Ca2+, which causes contraction
Nitric Oxide pathway
NO synthase makes NO (via conversion of L-arginine to L-citrulline), this activates guanylyl cyclase, whcih makes cGMP, which causes the vasodilation. Phosphodiesterase inactives cGMP into GMP.
when and how do platlets form?
- clotting normally occurs when there is damage to a blood vessel
- it immediately begins to adhere to the cut edges of the vessel and release chemicals that attract even more platelets
- a platelet plug is formed and external bleeding is stopped
what is fibrin?
a fibrous, non-globular protein
how is fibrin made?
protease (thrombin) on fibrinogen, hwihc causes it to plolymerize
role of fibrin
combines with platelets to form a hemostatic plug or clot over the wound site
